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Sculpture (mollusc)
Sculpture is a feature of many of the shells of mollusks. It is three-dimensional ornamentation on the outer surface of the shell, as distinct from either the basic shape of the shell itself or the pattern of colouration, if any. Sculpture is a feature found in the shells of gastropods, bivalves, and scaphopods. The word "sculpture" is also applied to surface features of the aptychus of ammonites, and to the outer surface of some calcareous opercula of marine gastropods such as some species in the family Trochidae. Sculpture can be concave or convex, incised into the surface or raised from it. Sometimes the sculpture has microscopic detailing. The term "sculpture" refers only to the calcareous outer layer of shell, and does not include the proteinaceous periostracum, which is in some cases textured even when the underlying shell surface is smooth. In many taxa, there is no sculpture on the shell surface at all, apart from the presence of fine growth lines. The sculp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epitonium Scalare
''Epitonium scalare'', common name the precious wentletrap, is a predatory or ectoparasitic species of marine gastropod with an operculum, in the family Epitoniidae, the wentletraps.Rosenberg, G. (2010). Epitonium scalare (Linnaeus, 1758). In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mollusca database. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=207942 on 2010-11-22 In the 17th and 18th century this was once considered to be a very rare shell and specimens changed hands for large sums of money. Johan de la Faille and Cosimo III de' Medici owned a wentletrap. Its habitat is subtidal in sand. Distribution This species is distributed in the Red Sea, in the Indian Ocean along Madagascar and South Africa, in the South West Pacific Ocean and along Fiji Islands and Japan. Shell description Adult shells of this species attain a length of between 25 mm to 72 mm. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convex
Convex or convexity may refer to: Science and technology * Convex lens, in optics Mathematics * Convex set, containing the whole line segment that joins points ** Convex polygon, a polygon which encloses a convex set of points ** Convex polytope, a polytope with a convex set of points ** Convex metric space, a generalization of the convexity notion in abstract metric spaces * Convex function In mathematics, a real-valued function is called convex if the line segment between any two distinct points on the graph of a function, graph of the function lies above or on the graph between the two points. Equivalently, a function is conve ..., when the line segment between any two points on the graph of the function lies above or on the graph * Convex conjugate, of a function * Convexity (algebraic geometry), a restrictive technical condition for algebraic varieties originally introduced to analyze Kontsevich moduli spaces Economics and finance * Convexity (finance), second ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Varix (mollusc)
A varix (: varices) is an anatomical feature of the gastropod shell, shell of certain sea snails, marine (ocean), marine gastropod molluscs. Gastropods whose shells have varices are primarily families and species within the Taxonomy (biology), taxonomic groups Littorinimorpha and Neogastropoda. The varix is a thickened axial ridge, a subcylindrical protrusion, in the Exoskeleton, shell which exists in some families of marine gastropods. It is an important shell character in generic classification. A varix is located at intervals around the Whorl (mollusc), whorl, and is formed by considerable thickening of the outer lip during a resting stage in the growth of the shell. In other words, in gastropods whose shells have varices, the shells are characterised by episodic growth - the shell grows in spurts, and during the resting phase the varix forms. In many gastropod whose shells have varices, for example the Cassinae, the varix is essentially merely a thickening and swelling of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aperture (mollusc)
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where the head-foot part of the body of the animal emerges for locomotion, feeding, etc. The term ''aperture'' is used for the main opening in gastropod shells, scaphopod shells, and also for ''Nautilus'' and ammonite shells. The word is not used to describe bivalve shells, where a natural opening between the two shell valves in the closed position is usually called a ''gape (bivalve), gape''. Scaphopod shells are tubular, and thus they have two openings: a main anterior aperture and a smaller posterior aperture. As well as the aperture, some gastropod shells have additional openings in their shells for respiration; this is the case in some Fissurellidae (keyhole limpets) where the central smaller opening at the apex (mollusc), apex of the shell is called an orifice, and in the Haliotidae (abalone) where the row of respiratory openings in the shell are also called orifices. In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Columella (gastropod)
The columella (meaning "little column") or (in older texts) pillar is a central anatomical feature of a coiled snail shell, a gastropod shell. The columella is often only clearly visible as a structure when the shell is broken, sliced in half vertically, or viewed as an X-ray image. The columella runs from the apex of the shell to the midpoint of the undersurface of the shell, or the tip of the siphonal canal in those shells which have a siphonal canal. If a snail shell is visualized as a cone of shelly material which is wrapped around a central axis, then the columella more or less coincides spatially with the central axis of the shell. In the case of shells that have an umbilicus (mollusc), umbilicus, the columella is a hollow structure. The columella of some groups of gastropod shells can have a number of plications or folds (the columellar fold, plaits or plicae), which are usually visible when looking to the inner lip into the Aperture (mollusc), aperture of the shell. These ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plait (gastropod)
A plait is an anatomical feature which is present on the shells of some snails, or gastropods. This sculpture occurs often in the shells of marine gastropod mollusks in the clade Neogastropoda, but it is also found in some pulmonate land snails. Plaits are folds on the columella (also known as the pillar or axis) at the center of the shell. The columella (meaning little column) is the central structure around which the whorl A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). In nature File:Photograph and axial plane floral diagra ...s of a coiled gastropod shell are coiled. The presence or absence of plaits, and the number of plaits, are characteristics used in the description of many gastropod molluscs, often enabling similar species to be separated and identified correctly. References * Powell A W B, ''New Zealand Mollusca'', Will ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lira (mollusc)
Lirae (singular lira) are fine lines or ridges (much finer than ribs) that are a sculptural feature of the outside of the shells of various organisms. The term is commonly applied to the shells of molluscs such as gastropods, bivalves and nautiloids. It can also be used to describe similar sculpture on the surface of the shells of brachiopods. In addition the word is used to describe fine linear elevations of shelly material within the outer lip of the aperture of some gastropod shell The gastropod shell is part of the body of many gastropods, including snails, a kind of mollusc. The shell is an exoskeleton, which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium ...s. The adjectival form of the word is "lirate". References Mollusc shells {{animal-anatomy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transverse Plane
A transverse plane is a plane that is rotated 90° from two other planes. Anatomy The transverse plane is an anatomical plane that is perpendicular to the sagittal plane and the dorsal plane. It is also called the axial plane or horizontal plane, especially in human anatomy, but horizontal plane can be misleading with other animals. The plane splits the body into a cranial (head) side and caudal (tail) side, so in humans the plane will be horizontal (dividing the body into superior and inferior sections) but in quadrupeds it will be vertical. Human anatomy Clinically relevant anatomical planes * Transverse '' thoracic plane'' * '' Xiphosternal plane'' (or xiphosternal junction) * '' Transpyloric plane'' * '' Subcostal plane'' * '' Umbilical plane'' (or transumbilical plane) * '' Supracristal plane'' * '' Intertubercular plane'' (or transtubercular plane) * '' Interspinous plane'' Associated structures * The transverse '' thoracic plane'' ** Plane through T4 & T5 verteb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bead
A bead is a small, decorative object that is formed in a variety of shapes and sizes of a material such as stone, bone, shell, glass, plastic, wood, or pearl and with a small hole for threading or stringing. Beads range in size from under 1 mm to over 1 cm in diameter. Beads represent some of the earliest forms of jewellery, with a pair of beads made from ''Nassarius'' sea snail shells dating to approximately years ago thought to be the earliest known example. 2] Beadwork is the art or craft of making things with beads. Beads can be woven together with specialized thread, strung onto thread or soft, flexible wire, or adhered to a surface (e.g. fabric, clay). Etymology The word "bead" derives from Old English ''gebed'', originally meaning "prayer", until transferred to small globular objects. This refers to the use of beads for counting repetitions of prayers, as in Christian Pater Noster cords and rosaries. Types Beads can be divided into several types of overlap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanical Stress
In continuum mechanics, stress is a physical quantity that describes forces present during deformation. For example, an object being pulled apart, such as a stretched elastic band, is subject to ''tensile'' stress and may undergo elongation. An object being pushed together, such as a crumpled sponge, is subject to ''compressive'' stress and may undergo shortening. The greater the force and the smaller the cross-sectional area of the body on which it acts, the greater the stress. Stress has dimension of force per area, with SI units of newtons per square meter (N/m2) or pascal (Pa). Stress expresses the internal forces that neighbouring particles of a continuous material exert on each other, while ''strain'' is the measure of the relative deformation of the material. For example, when a solid vertical bar is supporting an overhead weight, each particle in the bar pushes on the particles immediately below it. When a liquid is in a closed container under pressure, each par ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taxa
In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and given a particular ranking, especially if and when it is accepted or becomes established. It is very common, however, for taxonomists to remain at odds over what belongs to a taxon and the criteria used for inclusion, especially in the context of rank-based (" Linnaean") nomenclature (much less so under phylogenetic nomenclature). If a taxon is given a formal scientific name, its use is then governed by one of the nomenclature codes specifying which scientific name is correct for a particular grouping. Initial attempts at classifying and ordering organisms (plants and animals) were presumably set forth in prehistoric times by hunter-gatherers, as suggested by the fairly sophisticated folk taxonomies. Much later, Aristotle, and later st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Periostracum
The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods and bivalves, but it is also found in cephalopods such as ''Allonautilus scrobiculatus''. The periostracum is an integral part of the shell, and it forms as the shell forms, along with the other shell layers. The periostracum is used to protect the organism from corrosion. The periostracum is visible as the outer layer of the shell of many molluscan species from terrestrial, freshwater, and marine habitats, and may be seen in land snails, river mussels, and other kinds of freshwater bivalves, as well as in many kinds of marine shelled molluscs. The word ''periostracum'' means "around the shell", meaning that the periostracum is wrapped around what is usually the more calcareous part of the shell. Technically, the calcareous part of the sh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
